We want to relate the diversity of amino acid sequences among Hl histones to the role of Hl in the structure of the chromosome and to the dynamics of that structure in its various functions. The structural diversity of Hl histone will be observed by determining the amino acid sequences of several of them. The effects of individual species of Hl histone on the physical conformation of DNA and Hl-depleted chromatin fragments will be observed by circular dichroism, hydrodynamic methods, and electron microscopy. Non-histone proteins that may form specific complexes with particular kinds of Hl histones will be isolated and tested for specific interaction by observing the size of the putative complexes (gel sieve and chemical cross-linking). We will attempt to fractionate chromatin into euchromatin, heterochromatin (general) and centromeric chromatin and test for segregation of different species of Hl histone.